Modern wireless systems utilize multi-band and multi-mode operations to simultaneously support multiple different communication standards. These rapidly growing demands have posed tremendous challenges for future radio frequency (RF) transmitter development and especially power amplifiers (PA). One popular solution for multi-band PAs is to directly assemble several single-band PAs either in a chip or on a multiple-chip module. This approach, however, can have several drawbacks, such as large chip/module area, increased cost, dedicated antenna interface to each PAs, possible need of off-chip switches and complicated packaging. Tunable passive networks can also be utilized to achieve multi-band impedance matching and power combining for RF PAs. These tunable components often pose a direct trade-off among passive loss and frequency range and suffer from reliability concerns of tunable components such as varactors and switch-cap banks.